I used to do a lot of residential service changes and my method was to use split bolts, and then call the power company to have them come out and do the permanent splice..and while thay are at it they could re-seal the meter ring.
In the situation that you are describing it sounds like it will be just your baby, so you'll be stuck with split bolts. Just be sure to utilize the separator plate that comes with the split bolt (Ilsco type SK)and cinch it down real good (without stripping the threads!). If this subpanel installation is something you can re-visit once a year for checking the tightening, then you should have no problems.